A novel design of coplanar 8-bit ripple carry adder using field-coupled quantum-dot cellular automata nanotechnology

Abstract

Quantum-dot cellular automata (QCA) is a prominent research field that can replace MOS technology due to constraints of short-channel effects, power consumption and lithography costs. This manuscript presents novel and efficient designs of various combinational circuits that are XOR gate, half adders (HA), full adders (FA), half subtractor (HS), full subtractor (FS), ripple carry adder (RCA) and (2 x 1) multiplexer. This study presents an innovative concept for digital circuits that can be implemented in a single layer by using 90 & DEG; cells in clock zones. The suggested circuit architectures are relatively basic and straightforward to construct a robust QCA layout. One may reduce the overall size and the number of QCA cells by using the aforementioned designs and incorporating them into bigger circuits, such as the 4-bit and 8-bit RCA. Every design suggested in the study is compared to a design already published in the literature, and it is discovered that the suggested designs are much superior in terms of latency, area, number of cells and gate counts. QCADesigner tool confirms the functional correctness of proposed circuits. All newly created FAs, Design 1, Design 2, Design 3 and Design 4, exhibit cell count improvements of 18.88%, 40%, 46.66% and 4.44%, respectively, compared to the best-reported design. The area efficiency improves by up to 83.6% and 35.11%, respectively, while the cell count improves by 67.8% and 25.15% for 4-bit and 8-bit RCA adders, indicating that they are more suited for computational sciences.